Yes, that was stupid back then. No, this doesn't excuse it now, especially when it's so much more stupid.
Also, back then, it followed an important storytelling rule: The more impact an event has, the better it needs to be explained.
All the subspace shockwave did was break a coffee cup. Apart from that - the movie would have played out exactly the same if they just saw the explosion through a telescope. But ship shaking is a more dramatic opening. It WAS Kronos moon after all, and that was the only real lasting effect, and that one was well thought out.
But because that shockwave was a detail that had no impact, no body care that it was scientifically bunk.
But just imagine, of the subspace shockwave suddenly completely destroyed Earth? People would flip their shit! How the fuck that's even possible, and that it makes no fucking sense for such a large scale event to ever happen this way! Even though the bunk science would be the same.
Well. The same holds true for Romulus. If it were just a minor bit, people wouldn't take the science so serious. But having the biggest, universe-changing event happen so completely randomly for such utterly ducking stupid, inconsistent crap reasons, does affect story immersion.